Quantitative model-based high angle annular dark field scanning transmission electron microscopy.

Date: 6 January 2015

Venue: Campus Middelheim - Lokaal G0.10 - Middelheimlaan 1 - 2020 Antwerpen

Time: 4:00 PM

Organization / co-organization: Faculty of Sciences

PhD candidate: Gerardo Tadeo Martinez Alanis

Principal investigator: Sandra Van Aert & Jo Verbeeck

Short description: PhD defense Gerardo Tadeo Martinez Alanis - Faculty of Sciences

Abstract: New developments in the field of nanotechnology drive the need for advanced quantitative characterisation techniques of materials. The properties of a material are controlled by the specific atomic structure. Measuring the positions, atom types and number of atoms as accurately and precisely as possible is therefore an important challenge. The scanning transmission electron microscope (STEM) using a high angle annular dark field detector (HAADF) allows one to obtain images that are sensitive to the chemical and structural information of materials at the atomic level. In this thesis, quantitative model-based methods using statistical parameter estimation theory and image simulations are studied, applied and developed to extract quantitative information from HAADF STEM images. The quantification is carried out in a relative or absolute manner by combining statistics-based methods and image simulation-based methods. To reach this goal, so-called atomic column scattering cross-sections are used. An analysis of the image intensity contributions to the cross-sections is performed to explore the origins of their sensitivity to the atomic structure. This analysis results in a new normalisation method using electron flux weighting and a quality measure of the HAADF detector response.